Rasha M. El-Abassy

Scope and limitations of principal component analysis of high resolution LC-TOF-MS data: the analysis of the chlorogenic acid fraction in green coffee beans as a case study

Within this contribution we have analysed aqueous methanolic extracts by LC-ESI-TOF-MS of a total of 38 green bean coffee samples, which vary in terms of coffee variety and processing conditions. The LC-MS data have been analysed by principal component analysis (PCA) using different PCA processing parameters using an unsupervised non-targeted approach as well as a knowledge-based targeted approach. Furthermore, different normalisation and scaling algorithms have been applied to the PCA dataset. The scope and limitation of the various PCA parameters are discussed with respect to the ability to differentiate between samples of different groups, including different coffee varieties (Arabica or Robusta coffee) or different processing parameters and with respect to the information content of the PCA analysis on a molecular level. We could show that while distinction between different groups of samples can be successfully carried out independent of PCA parameters employed, identifying molecular markers rationalising differentiation between sample groups varies significantly between PCA parameters and requires careful choice as well as critical evaluation.

Direct Determination of Unsaturation Level of Milk Fat Using Raman Spectroscopy

We have demonstrated the potential of visible Raman spectroscopy in combination with chemometric analysis as a fast and simple tool for the determination of the unsaturation level of milk fat. The Raman measurements have been performed directly on liquid milk and on fat extracted from liquid milk. The Raman spectra taken from the extracted fat showed a higher resolution. The spectra directly obtained from the milk samples had some fluorescence background but nevertheless yielded the desired information. For calibration purposes, the iodine value (IV) was determined in all cases in order to evaluate the unsaturation level of the investigated samples. Two separate calibration models have been constructed; one for the milk samples and the second one for the extracted fat. The accuracy of these calibration models was estimated using the root mean square error of calibration and validation (RMSE) and the coefficient of determination (R 2 ) between actual and predicted values.

Vibrational spectroscopy and density functional theory analysis of 3-O-caffeoylquinic acid.

Density functional theory (DFT) calculations are being performed to investigate the geometric, vibrational, and electronic properties of the chlorogenic acid isomer 3-CQA (1R,3R,4S,5R)-3-{[(2E)-3-(3,4-dihydroxyphenyl)prop-2-enoyl]oxy}-1,4,5-trihydroxycyclohexanecarboxylic acid), a major phenolic compound in coffee. DFT calculations with the 6-311G(d,p) basis set produce very good results. The electrostatic potential mapped onto an isodensity surface has been obtained. A natural bond orbital analysis (NBO) has been performed in order to study intramolecular bonding, interactions among bonds, and delocalization of unpaired electrons. HOMO-LUMO studies give insights into the interaction of the molecule with other species. The calculated HOMO and LUMO energies indicate that a charge transfer occurs within the molecule.

Which spectroscopic technique allows the best differentiation of coffee varieties: comparing principal component analysis using data derived from CD-, NMR- and IR-spectroscopies and LC-MS in the analysis of the chlorogenic acid fraction in green coffee beans

In this contribution we have analysed aqueous methanolic extracts of a total of 38 green bean coffee samples, which vary in terms of the coffee variety and processing conditions. We have characterised these extracts using NMR-, IR- and CD-spectroscopies along with LC-MS. All spectroscopic data have been analysed by principal component analysis (PCA) using different PCA processing parameters by an unsupervised non-targeted approach. We could show that the distinction between different groups of samples, in particular, Arabica versus Robusta green coffee beans can be successfully analysed by IR-spectroscopy and LC-MS. Surprisingly both CD- and NMR-spectroscopies fail to achieve, in this case, an adequate level of distinction. This is, to the best of our knowledge, the first study that directly compares the value of various spectroscopic techniques if multivariant statistical techniques are employed to them.

Assessment of Microwave versus Conventional Heating Induced Degradation of Olive Oil by VIS Raman Spectroscopy and Classical Methods

Over the last few decades, the microwave heating process has experienced more common and routine use for both home and industrial applications. In industrial field, microwave heating has been used for many applications, including food processing and preservation, bleaching, pasteurization, and sterilization (Decareau, 1985; Farag et al., 2001; Knutson et al., 1987). Numerous advantages boosted the use of microwave heating making it in many cases a technique preferred to conventional heating. These advantages include precise timing, rapidity, and energy saving. The principle of microwave heating is based on the interaction of electromagnetic waves with the molecular constituents of food. Such interaction leads to heat generation in the entire volume at nearly the same rate due to internal thermal dissipation of the vibrational energy of the molecules in the food (Decareau, 1985; Kamel & Stauffer, 1993). On the contrary, conventional heating generates heat at the contact surface first, and then the heat diffuses inward. The effects of microwave heating and conventional heating on the food components are therefore expected to be completely different. Since processed foods by microwaves are heated as a result of molecular excitation (Stein, 1972), many researchers have been concerned with the evaluation of the effect of microwaves on food constituents, nutrient retention and the change of flavours and colours of heated food (Finot, 1995; Mudgett, 1982). Microwave heating of roasted seeds and beans shows a better retention of flavour and antioxidant compounds without any significant chemical changes of the lipids (Behera et al., 2004; H. Yoshida & Kajimoto, 1989, 1994). With respect to lipid components, microwave heating was studied to verify eventual heat induced effects on different oils and fats (Farag, 1994; Hiromi Yoshida et al., 1990; H. Yoshida et al., 1992). For this purpose, peroxide value, carbonyl value and conjugated diene and triene levels were assessed. Extra virgin olive oil that comes from the first pressing of the olive, without using heat or chemicals, contains natural antioxidants such as tocopherols, carotenoids, sterols, and phenolic compounds (Boskou, 1996). It should be mentioned that carotenoids play a significant role as antioxidants by scavenging free radicals, and as singlet oxygen quenchers (Burton & Ingold, 1984; Di Mascio et al., 1989). Since oil and fat have low specific heat constants and heat quickly (Jowitt, 1983), nowadays microwave frying of food has been

Poly(lactic acid)/Organo-Montmorillonite Nanocomposites: Synthesis, Structures, Permeation Properties and Applications

Polylactic acid (PLA)/organo-montmorillonite nanocomposites were prepared by the solution casting method using chloroform as solvent. The clays were organically modified by four different modifiers, ternary amine with two alkyl (tallow) tails, primary amine containing silane with a single tail, ammonium salt with a single alkyl (tallow) tail, and ammonium salts with two alkyl (tallow) tails. The structural characterization of the nanocomposite films was performed using Raman spectroscopy and the internal structure of the nanocomposites in the nanometer range was studied using wide-angle X-ray diffraction analysis. All the nanocomposites exhibited superior improvement when compared to neat PLA. Differential scanning calorimetry (DSC) was performed to study the thermal behavior of the prepared composites. Among the used clay types, M24 was the most effective in improving the water vapor and oxygen barrier properties. Water vapor and oxygen permeability of the nanocomposite films were decreased up to 80 and 49% when using M24 clay, respectively. Surface properties of the films were investigated with dynamic contact angle measurements. The migration studies of neat PLA and nanocomposites were performed for three types of food simulants.